Children born by C-section have higher risk of obesity later in life

Reasons for cesarean births are also risk factors for obesity, but new research suggests the procedure itself is also to blame.

Many of the circumstances that result in birth by caesarean section, including maternal obesity, are also obesity risk factors for children. So it’s no surprise that people born by C-section are more likely than others to be overweight in childhood and early adulthood. However, the C-section procedure itself may also increase the risk of obesity later in life, according to a new Harvard study appearing in JAMA Pediatrics. Audrey Gaskins is one of its coauthors. We asked her about the findings.

ResearchGate: Where did the data for this analysis come from?

Audrey Gaskins: The Growing Up Today Study (GUTS) is an ongoing prospective cohort study of young adults followed since 1996. A total of 16,882 children aged 9 to 14 years responded to the baseline questionnaire, and an additional 10,923 children aged 9 to 14 enrolled in 2004. Participants have been followed with yearly self-administered follow-up questionnaires between 1997 and 2001 and biennial questionnaires thereafter. The mothers of all of these children are also enrolled in our ongoing Nurses' Health Study II which, by linking the datasets, can provide rich, detailed information on maternal characteristics and pregnancy-related information.

RG: Why did you and your coauthors look specifically at cesarean births and obesity, and what did you find?

Gaskins: Our group’s original motivation to conduct this study was to show that the association between cesarean birth and higher risk of childhood obesity that others had reported was solely due to the fact that many of the reasons that cesareans are performed—such as maternal obesity, excessive weight gain during pregnancy, large babies, and gestational diabetes—are also risk factors for childhood obesity. We expected that after controlling for these other risk factors in our analysis, the association between cesarean birth and childhood obesity would completely disappear. That was not the case. In fact, when we performed sensitivity analyses to further minimize this type of bias the results not only persisted but became stronger.

We found that individuals born by cesarean were more likely to become obese as children and adolescents, and to remain obese as young adults. What makes our findings compelling and different from previous studies addressing this question, is that this was also true when we compared siblings who differed in type of delivery—one was born by cesarean and the other by vaginal delivery—and when restricted to women without any known risk factors for having a cesarean, some of whom may have undergone elective cesarean.

RG: What other factors did you adjust for?

Gaskins: We adjusted for maternal age at delivery, race, region of birth, pre-pregnancy BMI, maternal height, gestational diabetes, pre-eclampsia, pregnancy induced hypertension, gestational age at delivery, birth weight, pre-pregnancy smoking, previous Cesarean section, offspring sex, and birth order. All of these variables have been associated with both cesarean sections and offspring obesity.

RG: Why do you think children born by cesarean are more likely to be obese?

Gaskins: The most compelling mechanism supporting this association is differences in gut microbiota. At birth, our bodies are colonized by bacteria. Children born by vaginal delivery are primarily exposed to their mothers' vaginal and gut microbes, whereas children born by cesarean are primarily exposed to bacteria on their mothers' skin and whatever bacteria happen to be in the air in the operating room. This initial difference in mode of delivery leads to changes in the type of bacteria living in children’s guts. Moreover, the pattern of gut bacteria that children born by C-section tend to have has been previously linked to greater risk of obesity later in life.

RG: Is this something doctors and parents should consider when deciding whether a cesarean birth is the right option?

Gaskins: Cesareans are an essential and lifesaving procedure in many cases, but they are not always necessary—and they are not risk free. If there is not a clear medical or obstetric indication for having a cesarean delivery, women should talk with their doctors about the potential risks to both themselves and their children, one of which is a higher risk of obesity for the child.

RG: What are the next steps for this research?

Gaskins: We are hoping to follow-up on the hypothesis that differences in gut microbiota are explaining the increased risk of obesity we see in individuals born via C-section. Studies documenting differences in microbiota according to mode of delivery have mainly been limited to the first year of life. Thus, whether differences in offspring microbiota are sustained long-term still remains to be evaluated.